1. Field of the Invention
This invention pertains to retaining drilling fluid within the mud system of a drilling operation when there is a reduction or loss of pressure in the part of the mud circulating in the drill string or when the drill string is separated to add a new joint of pipe and specifically pertains to preventing spilling such fluid from the portion of the mud circulation system remaining in the part of the pipe assembly disconnected from the drill string when there is an addition of a new pipe joint.